1. Field of the Invention
This invention relates to a rotation shaft seal, especially, a rotation shaft seal used for sealing high pressure fluid such as gas.
2. Description of the Related Art
Conventionally, a rotation shaft seal of this kind, as shown in FIG. 6, is provided with a seal member 43 of rubber which is disposed between a housing 41 and a rotation shaft 42 and having a lip end portion 44 extending to a fluid storing chamber 47 as to diminish in diameter. The lip end portion 44 has a contact portion 46 which contacts a peripheral face of the rotation shaft 42 and an end face 45 facing the rotation shaft 42 with an acute angle θ. The contact portion 46 and the end face 45 of the lip end portion 44, having configurations smoothly changing from a round convex to a straight line, are widely used.
As shown in FIG. 6, when the pressure of the fluid sealed in the fluid storing chamber 47 is high, contact pressure of the contact portion 46 of the lip end portion 44 on the rotation shaft 42 becomes high. And, when the rotation frequency of the rotation shaft 42 is high, sealing ability is decreased because the contact portion 46 is rapidly abraded by friction on the rotation shaft 42.
It is therefore an object of the present invention to provide a rotation shaft seal having high durability in which the abrasion of the contact portion of the seal member for sealing is reduced even if the pressure of the sealed fluid is high.